A study at Temple University School of Medicine found that lying takes more brain energy than telling the truth. Participants were divided into two groups. Those in the first group were asked to shoot a toy gun and then lie and say they didn't do it. Those in the second group watched what happened and then told the truth about it. An MRI machine indicated that the liars had to use seven areas of the brain in their response. By comparison, those who told the truth only used four areas of the brain.